| 1. |
- Almgren, Torgny, 1962, et al.
(författare)
-
Optimization models for improving periodic maintenance schedules by utilizing opportunities
- 2012
-
Ingår i: Proceedings of 4th Production and Operations Management World Conference, July 2012.
-
Konferensbidrag (refereegranskat)abstract
- We present mathematical models for finding optimal opportunistic maintenance schedules for systems, in which components are assigned maximum replacement intervals. Our mod- els are applied to safety-critical components in an aircraft engine, for which maintenance opportunities naturally arise since entire modules are sent to the workshop when mainte- nance is required on one or more components. Case study results illustrate the advantage of the mathematical models over simpler policies, the benefit of coordinating the maintenance in economically dependent systems, and that our models can be utilized also for strategic investment decision support.
|
|
| 2. |
- Almgren, Torgny, 1962, et al.
(författare)
-
Optimization of opportunistic replacement activities: A case study in the aircraft industry
- 2007
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In the aircraft industry maximizing availability is essential. Maintenance schedules must therefore be opportunistic, incorporating preventive maintenance activities within the scheduled as well as the unplanned ones. At the same time, the maintenance contractor should utilize opportunistic maintenance to enable the minimization of the total expected cost to have a functional aircraft engine and thus to provide attractive service contracts. This paper provides an opportunistic maintenance optimization model which has been constructed and tested together with Volvo Aero Corporation in Trollhättan, Sweden for the maintenance of the RM12 engine. The model incorporates components with deterministic as well as with stochastic lives. The replacement model is shown to have favourable properties; in particular, when the maintenance occasions are fixed the remaining problem has the integrality property, the replacement polytope corresponding to the convex hull of feasible solutions is full-dimensional, and all the necessary constraints for its definition are facet-inducing. We present an empirical crack growth model that estimates the remaining life and also a case study that indicates that a non-stationary renewal process with Weibull distributed lives is a good model for the recurring maintenance occasions. Using one point of support for the distribution yields a deterministic replacement model; it is evaluated against classic maintenance policies from the literature through stochastic simulations. The deterministic model provides maintenance schedules over a finite time period that induce fewer maintenance occasions as well as fewer components replaced.
|
|
| 3. |
|
|
| 4. |
- Almgren, Torgny, 1962, et al.
(författare)
-
The opportunistic replacement problem: analysis and case studies
- 2011
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We consider an optimization model for determining optimal opportunistic maintenance (that is, component replacement) schedules when data is deterministic. This problem generalizes that of Dickman, Epstein, and Wilamowsky [21] and is a natural starting point for the modelling of replacement schedules when component lives are non-deterministic. We show that this basic opportunistic replacement problem is NP-hard. We show that the convex hull of the set of feasible replacement schedules is full-dimensional, and that all the necessary inequalities also are facet-inducing. We show that when maintenance occasions are fixed, the remaining problem can be stated as a linear program; when maintenance costs are monotone with time, the latter is solvable through a greedy procedure. Results from a series of case studies performed in the areas of aircraft engine and wind turbine maintenance are also reported. These illustrate the advantages of utilizing opportunistic maintenance activities based on a complete optimization model, as compared to simpler policies.
|
|
| 5. |
- Almgren, Torgny, 1962, et al.
(författare)
-
The opportunistic replacement problem: theoretical analyses and numerical tests
- 2012
-
Ingår i: Mathematical Methods of Operations Research. - : Springer Science and Business Media LLC. - 1432-2994 .- 1432-5217. ; 76:3, s. 289-319
-
Tidskriftsartikel (refereegranskat)abstract
- We consider a model for determining optimal opportunistic maintenance schedules with respect to a maximum replacement interval. This problem generalizes that of Dickman et al. (J Oper Res Soc India 28:165–175, 1991) and is a natural starting point for modelling replacement schedules of more complex systems. We show that this basic opportunistic replacement problem is NP-hard, that the convex hull of the set of feasible replacement schedules is full-dimensional, that all the inequalities of the model are facet-inducing, and present a new class of facets obtained through a {0,1/2}-Chvátal–Gomory rounding. For costs monotone with time, a class of elimination constraints is introduced to reduce the computation time; it allows maintenance only when the replacement of at least one component is necessary. For costs decreasing with time, these constraints eliminate non-optimal solutions. When maintenance occasions are fixed, the remaining problem is stated as a linear program and solved by a greedy procedure. Results from a case study on aircraft engine maintenance illustrate the advantage of the optimization model over simpler policies. We include the new class of facets in a branch-and-cut framework and note a decrease in the number of branch-and-bound nodes and simplex iterations for most instance classes with time dependent costs. For instance classes with time independent costs and few components the elimination constraints are used favorably. For fixed maintenance occasions the greedy procedure reduces the computation time as compared with linear programming techniques for all instances tested.
|
|
| 6. |
- Almgren, Torgny, 1962, et al.
(författare)
-
The replacement problem: A polyhedral and complexity analysis. The complete version
- 2009
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We consider an optimization model for determining optimal opportunistic maintenance (that is, component replacement) schedules when data is deterministic. This problem, which generalizes that of Dickman et al., is a natural starting point for the modelling of replacement schedules when component lives are non-deterministic, whence a mathematical study of the model is of large interest. We show that the convex hull of the set of feasible replacement schedules is full-dimensional, and that all the necessary inequalities are facet-inducing. Additional facets are then provided through Chvatal-Gomory rounding. We show that when maintenance occasions are fixed, the remaining problem reduces to a linear program; in some cases the latter is solvable through a greedy procedure. We further show that this basic replacement problem is NP-hard.
|
|
| 7. |
- Fotedar, Sunney, 1989, et al.
(författare)
-
A criterion space decomposition approach to generalized tri-objective tactical resource allocation
- 2023
-
Ingår i: Computational Management Science. - : Springer Science and Business Media LLC. - 1619-697X .- 1619-6988. ; 20:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present a tri-objective mixed-integer linear programming model of the tactical resource allocation problem with inventories, called the generalized tactical resource allocation problem (GTRAP). We propose a specialized criterion space decomposition strategy, in which the projected two-dimensional criterion space is partitioned and the corresponding sub-problems are solved in parallel by application of the quadrant shrinking method (QSM) (Boland in Eur J Oper Res 260(3):873–885, 2017) for identifying non-dominated points. To obtain an efficient implementation of the parallel variant of the QSM we suggest some modifications to reduce redundancies. Our approach is tailored for the GTRAP and is shown to have superior computational performance as compared to using the QSM without parallelization when applied to industrial instances.
|
|
| 8. |
- Fotedar, Sunney, 1989, et al.
(författare)
-
A decision-making tool to identify routings for an efficient utilization of machining resources: the decision makers’ perspective
- 2020
-
Ingår i: PLANs forsknings-och tillämpningskonferens.
-
Konferensbidrag (refereegranskat)abstract
- In the aerospace industry, efficient management of machining capacity is crucial to meet the required service levels to customers (which includes, measures of quality and lead-times ) and keeps the tied-up working capital in check. The proposed decision-making tool, described in this paper, aims to combine information and knowledge of manufacturing and logistics experts in a company to improve flow of materials through the factory. The material flow situation is different for a large aerospace tier-1 supplier as opposed to flow-based manufacturing company; when there is no pandemic or natural calamity, having relatively stable demand due to long-term contract is common, but there exists short-term demand variability. There is a complex flow of products at GKN Aerospace, as the products share machining resources, thus, resulting in uneven loads at machines and sometimes excess loading at certain machines. This along with short-term demand variability results in long queues in-front of machines which contributes with the biggest share of the total lead-time. Thus, long waiting times at one/many machine/s is common and may lead to bottlenecks in many places in the production pipeline. So, there is potential benefit in having rerouting-flexibility for products which can help in reducing queuing. However, qualifying a product for a new machine is time-consuming activity, and thus, should be done few years in advance. We propose a mathematical model aimed at improving some of these deficiencies of commonly used methods by facilitating balanced resource loading levels, i.e. to provide more degrees of freedom to the planner to absorb demand variations. The output provided by the model includes production routings in each time period (quarter) for the next 4–5 years; new qualifications to be done by technical staff for allocation of part types/products to machines which are not yet qualified/used for a given product. We keep the resource loading levels that are above a given threshold as low as possible and reduce the time/money spent for qualifying new allocations.
|
|
| 9. |
- Fotedar, Sunney, et al.
(författare)
-
Bi-objective optimization of the tactical allocation of job types to machines: mathematical modeling, theoretical analysis, and numerical tests
- 2022
-
Ingår i: International Transactions in Operational Research. - : Wiley. - 0969-6016 .- 1475-3995.
-
Tidskriftsartikel (refereegranskat)abstract
- We introduce a tactical resource allocation model for a large aerospace engine system manufacturer aimed at long-term production planning. Our model identifies the routings a product takes through the factory, and which machines should be qualified for a balanced resource loading, to reduce product lead times. We prove some important mathematical properties of the model that are used to develop a heuristic providing a good initial feasible solution. We propose a tailored approach for our class of problems combining two well-known criterion space search algorithms, the bi-directional epsilon-constraint method and the augmented weighted Tchebycheff method. A computational investigation comparing solution times for several solution methods is presented for 60 numerical instances.
|
|
| 10. |
- Fotedar, Sunney, 1989, et al.
(författare)
-
Mathematical optimization of the tactical allocation of machining resources for an efficient capacity utilization in aerospace component manufacturing
- 2019
-
Ingår i: Proceedings of the 10th Aerospace Technology Congress. - : Linköping University Electronic Press. - 1650-3686 .- 1650-3740. - 9789175190068 ; , s. 183-188
-
Konferensbidrag (refereegranskat)abstract
- In the aerospace industry, with low volumes and many products, there is a critical need to efficiently use available manufacturing resources. Currently, at GKN Aerospace, resource allocation decisions that in many cases will last for several years are to some extent made with a short-term focus so as to minimize machining time, which results in a too high load on the most capable machines, and too low load on the less capable ones. This creates an imbalance in capacity utilization that leads to unnecessary queuing at some machines, resulting in long lead times and in an increase in tied-up capital. Tactical resource allocation on the medium to long-range planning horizon (six months to several years) aims to address this issue by allocating resources to meet the predicted future demand as effectively as possible, in order to ensure long range profitability. Our intent is to use mathematical optimization to find the best possible allocations.
|
|
| 11. |
- Fotedar, Sunney, et al.
(författare)
-
Robust optimization of a bi-objective tactical resource allocation problem with uncertain qualification costs
- 2022
-
Ingår i: Autonomous Agents and Multi-Agent Systems. - : Springer Science and Business Media LLC. - 1387-2532 .- 1573-7454. ; 36:2
-
Tidskriftsartikel (refereegranskat)abstract
- In the presence of uncertainties in the parameters of a mathematical model, optimal solutions using nominal or expected parameter values can be misleading. In practice, robust solutions to an optimization problem are desired. Although robustness is a key research topic within single-objective optimization, little attention is received within multi-objective optimization, i.e. robust multi-objective optimization.This work builds on recent work within robust multi-objective optimization and presents a new robust efficiency concept for bi-objective optimization problems with one uncertain objective. Our proposed concept and algorithmic contribution are tested on a real-world multi-item capacitated resource planning problem, appearing at a large aerospace company manufacturing high precision engine parts. Our algorithm finds all the robust efficient solutions required by the decision-makers in significantly less time than the approach of Kuhn et al. (Eur J Oper Res 252(2):418-431, 2016) on 28 of the 30 industrial instances.
|
|
| 12. |
- Strömberg, Ann-Brith, 1961, et al.
(författare)
-
Optimering av underhållsplaner leder till strategier för utvecklingsprojekt
- 2008
-
Ingår i: Logistikutveckling - teori möter praktik, artiklar från PLANs Forsknings- och tillämpningskonferens, 27-28 augusti 2008, Göteborg. ; , s. 169-180
-
Konferensbidrag (refereegranskat)abstract
- Inom många typer av industriell verksamhet, t ex process-, kraft- och flygindustri, används dyrbar produktionsutrustning som måste vara tillgänglig i mycket hög utsträckning eftersom produktionsstopp är mycket kostsamma. För att dessa industrier ska kunna maximera lönsamheten måste de kunna utnyttja produktionsstopp för att även utföra bästa möjliga förebyggande underhåll. Chalmers Matematik och Volvo Aero har tillsammans utvecklat en matematisk modell som ser till ekonomiska och funktionella samband mellan komponenter i det system som skall underhållas, samt kostnader för underhållsaktiviteter och reservdelar. En studie utförd i en verkstad för underhåll av flygmotorer vid Volvo Aero visar på en signifikant potential för kostnadsbesparingar som till stor del beror av ökade möjligheter till aktiv samordning av framtida underhåll via balansering av komponenternas livslängder. Studien har även medfört en nyttig genomlysning av systemet. Den visar att möjligheten att reducera underhållskostnader i hög grad beror på livslängderna hos de i systemet ingående komponenterna. Olika komponenter har därför olika potential för reduktion av underhållskostnader. Dessa potentialer kan beräknas genom optimering av en serie modeller där livslängden för de olika delarna – var för sig – har förlängts stegvis. På detta sätt kan optimering av underhållsplaner även utnyttjas för att skapa beslutsunderlag för val av utvecklingsprojekt som syftar till att förlänga livslängder hos enskilda komponenter.
|
|
| 13. |
- Thörnblad, Karin, 1971, et al.
(författare)
-
A competitive iterative procedure using a time-indexed model for solving flexible job shop scheduling problems
- 2013
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We investigate the efficiency of a discretization procedure utilizing a time-indexed mathematical optimization model for finding accurate solutions to flexible job shop scheduling problems considering objectives comprising the makespan and the tardiness of jobs, respectively. The time-indexed model is used to find solutions to these problems by iteratively employing time steps of decreasing length. The solutions and computation times are compared with results from a known benchmark formulation and an alternative, slightly enhanced version of the same. For the largest instances---considering both objectives---the proposed method finds significantly better solutions than the other models within the same time frame, although there is a large difference in the performance of the models depending on which objective is considered. This implies that the evaluation of scheduling algorithms must be performed with respect to an objective that is suitable for the real application for which they are intended. The minimization of the makespan is no such objective, although it is the most widely used objective in research. We propose an objective incorporating tardiness. The iterative procedure for solving the time-indexed model outperforms the other models regarding the time to find the best feasible solution. We conclude that our iterative procedure with the time-indexed model is competitive with state-of-the-art mathematical optimization models. Since the proposed procedure quickly finds solutions of good quality to large instances, our findings imply that the new procedure is beneficially utilized for scheduling real flexible job shops.
|
|
| 14. |
|
|
| 15. |
- Thörnblad, Karin, 1971, et al.
(författare)
-
An efficient algorithm for solving the flexible job shop scheduling problem
- 2013
-
Ingår i: 25th NOFOMA conference proceedings, June 3-5 2013, Göteborg, Sweden.
-
Konferensbidrag (refereegranskat)abstract
- Purpose: To investigate the efficiency of a discretization procedure utilizing a time-indexed mathe-matical optimization model for finding accurate solutions to flexible job shop scheduling problems considering objectives comprising makespan and tardiness, respectively. Design/methodology/approach: A time-indexed mixed integer programming model is used to find solutions by iteratively employing time steps of decreasing length. The solutions and computation times are compared with results from a known benchmark formulation and an alternative model. Findings: The proposed method finds significantly better solutions for the largest instances within the same time frame. Both the other models are better choices for some smaller instances, which is expected since the new method is designed for larger problems. Only our alter-native model is able to solve two of the largest instances when minimizing the tardiness. Research limitations/implications: Interesting future research topics include the introduction of constraints representing other relevant entities such as the availability of tools and fixtures, and the scheduling of maintenance activities and personnel. Practical implications: Real cases of flexible job shop problems typically yield very large models. Since the new procedure quickly finds solutions of good quality to such instances, our findings imply that the new procedure is beneficially utilized for scheduling real flexible job shops. Original/value: We show that real flexible job shop problems can be solved through the solution of a series of carefully formulated discretized mathematical optimization models.
|
|
| 16. |
- Thörnblad, Karin, 1971, et al.
(författare)
-
Mathematical modelling of a real flexible job shop in aero engine component manufacturing
- 2011
-
Ingår i: Proceedings of 10th Workshop on Models and Algorithms for Planning and Scheduling Problems, June 2011, Nymburk, Czech Republic.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We formulate two mixed integer programming models stemming from a real flexible job shop problem with a total of ten resources and five main processing multipurpose machines. The models are compared w.r.t. memory usage, computation times, and accuracy.
|
|
| 17. |
- Thörnblad, Karin, 1971, et al.
(författare)
-
Mathematical optimization of a flexible job shop problem including preventive maintenance and availability of fixtures
- 2012
-
Ingår i: Proceedings of the 4th World P&OM Conference / 19th International Annual EurOMA Conference, Amsterdam, Netherlands, July 2012.
-
Konferensbidrag (refereegranskat)abstract
- The multitask cell at Volvo Aero Corporation is a flexible job shop containing ten resources aimed at being flexible with regard to product mix and processing types. Computing schedules for this type of job shop is an NP-hard problem. The computation times will therefore always be an issue, especially as the scheduling problem includes limited availability of fixtures and preventive maintenance planning. Computational results show that with the method developed we are able to produce optimal, or near-optimal, schedules for real data instances within an acceptable time frame. The scheduling principle proposed shortens lead times and minimizes tardiness.
|
|
| 18. |
- Thörnblad, Karin, 1971, et al.
(författare)
-
Optimering av scheman för en verklig produktionscell: tidsdiskretisering reducerar lösningstiden utan att lösningarnas kvalitet försämras
- 2011
-
Ingår i: PLANs forsknings- och tillämpningskonferens, 31 aug-1 sep 2011, Norrköping, Sverige.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Vid optimering av industriella schemaläggningsproblem är kompromissen mellan beräkningstid och resultatnivå ofta kritisk, med risken att en optimeringsmodell förenklas så mycket att dess resultat inte är praktiskt relevant. I artikeln jämförs två matematiska optimeringsmodeller för optimal schemaläggning av en verklig produktionscell på Volvo Aero. I den ena modellen beskrivs bl. a. operationers starttider m.h.a. kontinuerliga variabler, medan tiden har diskretiserats i den andra modellen. Diskretiseringen innebär att planeringshorisonten indelas i ett antal tidssteg, här kallade diskreta tidsperioder. Det är en förenkling eftersom all indata då måste uttryckas i helt antal diskreta tidsperioder och varje operation endast kan schemaläggas vid början av en tidsperiod. Den senare modellen visade sig överlägsen vad gäller beräkningstider och bedömdes därför ha mycket stor potential, trots risken för approximeringsfel p.g.a. tidsdiskretiseringen. 2 I artikeln presenteras tester med verkliga indata, vilka visar att approximeringsfelen blir mycket små när den diskreta tidsperiodens längd är en timma eller mindre, trots att några operationstider är kortare än så. Det optimala schemat från den tidsdiskreta modellen har före jämförelsen justerats så att alla operationstider är de ursprungliga, detta utan att förändra vare sig maskinval eller valda sekvenser på maskinerna. Denna modell har goda förutsättningar att fungera praktiskt, eftersom den både är snabb och ger goda resultat.
|
|
| 19. |
- Thörnblad, Karin, 1971, et al.
(författare)
-
Optimization of schedules for a multitask production cell
- 2010
-
Ingår i: Proceedings of The 22nd NOFOMA Conference in Kolding, Denmark, 10-11th of June 2010.
-
Konferensbidrag (refereegranskat)abstract
- Purpose of this paper; To optimize production schedules of a real production cell containing multi-purpose machines working as a job-shop in a complex logistic environment producing aircraft engine components. The planning and control of the production in the so called multitask cell results in a complex combinatorial problem. Design/methodology/approach; A mathematical optimization model of the multitask cell has been developed and tested on real data instances. The current production planning prerequisites have been studied in order to choose an appropriate objective function. Findings; Production plans resulting from the optimization model, are compared with schedules formed by the First in First Out (FIFO) and Earliest Due Date (EDD) priority rules, which are similar to the current manual planning of the multitask cell. Practical implications; The proposed scheduling principle will shorten lead times, and provide a more efficient use of the resources of the multitask cell. The effects are most significant at times with high utilization of the cell. What is original/value of paper; The development of theory and practice of optimization, together with the development of computer hardware during the past decades, enable the utilization of optimization as a tool for computing efficient production schedules in a complex logistic environment.
|
|
| 20. |
- Thörnblad, Karin, 1971, et al.
(författare)
-
Scheduling optimization of a real flexible job shop including fixture availability and preventive maintenance
- 2015
-
Ingår i: European Journal of Industrial Engineering. - 1751-5254 .- 1751-5262. ; 9:1, s. 126-145
-
Tidskriftsartikel (refereegranskat)abstract
- The multitask cell at GKN Aerospace Sweden is a flexible job shop containing ten resources aimed at being flexible with regard to product mix and processing types. We present a time-indexed formulation of the problem of optimally scheduling the planned jobs on the resources, also considering a limited availability of fixtures as well as required preventive maintenance activities. The objective is to minimize a weighted sum of the completion times and tardiness for the jobs, where the tardiness weight for a given job is a non-increasing function of its due date. We propose a fast iterative approach to finding a suitable value of the length of the time horizon that needs to be set for the time-indexed formulation and which considerably influences the computation time. Computational results show that the method developed is able to produce optimal, or near-optimal, schedules for real data instances within an acceptable practical time frame.
|
|
| 21. |
- Thörnblad, Karin, 1971, et al.
(författare)
-
Scheduling optimization of a real flexible job shop including side constraints regarding maintenance, fixtures, and night shifts
- 2013
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We present a generic iterative scheduling procedure for the scheduling of a real flexible job shop, the so-called multitask cell at GKN Aerospace Engine Systems in Sweden. A time-indexed formulation of the problem is presented including side constraints regarding preventive maintenance, fixture availability, and unmanned night shifts. This paper continues the work in [35], with an improvement of the iterative solution procedure and the inclusion of constraints regarding night shifts during which only unmanned processing is allowed. The resulting schedules are compared with schedules constructed using two priority dispatching rules. Computational results show that the gain of including the night shifts constraints is significant and that the methodology developed is able to produce near-optimal schedules for industrial data instances for the coming shift within an acceptable practical time frame.
|
|
| 22. |
- Thörnblad, Karin, 1971, et al.
(författare)
-
Scheduling optimization of a real flexible job shop including side constraints regarding maintenance, fixtures, and night shifts
- 2015
-
Ingår i: Proceedings of the 7th Multidisciplinary International Conference on Scheduling: Theory and Applications (MISTA 2015). 25 -28 Aug 2015, Prague, Czech Republic. - 2305-249X. ; , s. 78-101
-
Konferensbidrag (refereegranskat)abstract
- We present a generic iterative procedure for the scheduling of a real flexible job shop, the so-called multitask cell at GKN Aerospace Engine Systems in Sweden. A time-indexed formulation of the scheduling problem is presented—including side constraints regarding preventive maintenance, fixture availability, and unmanned night shifts. This paper continues the work in ”Scheduling optimization of a real flexible job shop including fixture availability and preventive maintenance” [Thörnblad et al., European Journal of Industrial Engineering, 2015], with an improvement of the iterative solution procedure, and the inclusion of constraints regarding night shifts during which only unmanned processing is allowed to be scheduled. Schedules resulting from our procedure and from the use of two priority dispatching rules are compared. The gain of including the night shifts constraints is significant. Despite the added complexity, our methodology produces near-optimal schedules for industrial data instances for the coming shift within an acceptable practical time frame.
|
|
| 23. |
- Vallhagen, Johan, 1965, et al.
(författare)
-
Advanced use of Data as an Enabler for Adaptive Production Control using Mathematical Optimization – An Application of Industry 4.0 Principles
- 2017
-
Ingår i: Procedia Manufacturing. - : Elsevier BV. - 2351-9789. ; 11, s. 663-670
-
Konferensbidrag (refereegranskat)abstract
- This paper deals with the need for more advanced and mathematically based planning and scheduling tools for production systems with complex flows which are subjected to constant change. To develop and utilise such tools, better data acquisition and aggregation from the operational level on the shop floor is needed. An information infrastructure has been proposed to enable this novel type of optimized adaptive scheduling to achieve significant improvements in production efficiency. The solution is based on a system architecture and an information infrastructure with a middleware that provides a specific production cell with all the data relevant for scheduling.
|
|
